Rep. Gabrielle Giffords has started to breathe on her own and doctors at the Tucson University Medical Center said Tuesday they continue to be optimistic about her recovery.

UMC Chief of Neurosurgery Dr. Michael Lemole said on NBC&rsquo;s &ldquo;Today&rdquo; show that Giffords had given doctors a &ldquo;thumbs up&rdquo; in response to questions, and that at one point she attempted to reach for her breathing tube. That, Lemole said, suggests the Arizona Democrat is in some discomfort which, medically speaking, is a good thing.

&ldquo;The fact that she&rsquo;s able to register that discomfort and then react to it, again, it means the brain is working on a higher level,&rdquo; he said.

Lemole also said that there has been no significant swelling in her brain at this point, which is a key indicator that she is progressing well.

He also said that while Giffords is now able to breathe on her own, the timeline for her recovery remains unclear. &ldquo;She&rsquo;s going to take her recovery at her own pace,&rdquo; he said.